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J. Org. Chem. 2001, 66, 3356-3361
Biosynthetic Studies on the Cyclopentane Ring Formation of Allosamizoline, an Aminocyclitol Component of the Chitinase Inhibitor Allosamidin Shohei Sakuda,*,1a Yasumasa Sugiyama,1a Ze-Yang Zhou,1b,d Hiroaki Takao,1b Hiroyuki Ikeda,1a Katsumi Kakinuma,1c Yasuhiro Yamada,1b,e and Hiromichi Nagasawa1a Department of Applied Biological Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan, Department of Biotechnology, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan, and Department of Chemistry, Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152-8551, Japan
[email protected] Received November 16, 2000
Allosamizoline (1) is an aminocyclitol component of allosamidin, a Streptomyces metabolite, and has a cyclopentane ring originated from D-glucosamine. Biosynthesis of the cyclopentane ring was studied by feeding experiments with a variety of deuterium-labeled glucosamine and glucose. In the feeding experiments with [3-2H]- and [4-2H]-D-glucosamine and [1-2H]-D-glucose, deuterium was incorporated into C-3, C-4, and C-1 of 1, respectively. On the other hand, feeding experiments with [5-2H]- and [6,6-2H2]-D-glucosamine showed that deuterium on C-5 and one of the two deuterium atoms on C-6 of glucosamine were lost during the cyclopentane ring formation of 1. In the feeding experiments with (6R)- and (6S)-[6-2H1]-D-glucose, the (6R)-deuterium of glucose was incorporated into the proS position on C-6 of 1, but the (6S)-deuterium of glucose was not incorporated into 1. These results suggested that an intermediate with a 6-aldehyde group is involved in the biosynthesis of the cyclopentane ring moiety of 1 and overall inversion of stereochemistry of the C-6 methylene group occurred by stereospecific oxidation and reduction on C-6 during the formation of 1. The 6-aldehyde intermediate may play a key role in the biosynthetic step(s) of cyclization to form the cyclopentane ring and/or deoxygenation at C-5. Allosamidin, a Streptomyces metabolite, is an inhibitor of family 18 chitinases and has a pseudotrisaccharide structure (Figure 1) consisting of two units of N-acetylD-allosamine and one unit of an aminocyclitol derivative, allosamizoline (1).2 Allosamizoline has a cyclopentanoid structure, which is highly oxygenated and fused with a dimethylaminooxazoline ring. Our biosynthetic studies on allosamidin revealed that the carbon skeleton of each allosamine and the cyclopentane moiety of 1 is derived from D-glucose, and D-glucosamine is their close precursor.3 Furthermore, we showed that the nitrogen atom on C-2 and the carbon skeleton of each moiety originate from an intact D-glucosamine molecule. A cyclopentanoid skeleton biosynthesized from carbohydrate is uncommon in natural products compared with a cyclohexanoid skeleton, but several compounds with important biological activities are known to have a cyclopentanoid skeleton * FAX: +81-3-5841-8022. (1) (a) The University of Tokyo. (b) Osaka University. (c) Tokyo Institute of Technology. (d) Present address: Southwest Agricultural University, Beibei, ChongQing 400716, China. (e) Present address: Department of Applied Biological Science, Faculty of Engineering, Fukuyama University, Sanzo, Gakuencho, Fukuyamashi, Hiroshima 729-0292, Japan. (2) (a) Sakuda, S.; Isogai, A.; Matsumoto, S.; Suzuki, A. J. Antibiot. 1987, 40, 296-300. (b) Sakuda, S.; Isogai, A.; Matsumoto, S.; Suzuki, A.; Koseki, K. Tetrahedron Lett. 1986, 27, 2475-2478. (c) Sakuda, S.; Isogai, A.; Makita, T.; Matsumoto, S.; Koseki, K.; Kodama, H.; Suzuki, A. Agric. Biol. Chem. 1987, 51, 3251-3259. (d) Sakuda, S.; Isogai, A.; Matsumoto, S.; Suzuki, A.; Koseki, K.; Kodama, H.; Yamada, Y. Agric. Biol. Chem. 1988, 52, 1615-1617. (e) Sakuda, S.; Isogai, A.; Suzuki, A.; Yamada, Y. Actinomycetologica 1993, 7, 50-57. (3) Zhou, Z.-Y.; Sakuda, S.; Yamada, Y. J. Chem. Soc., Perkin Trans. 1 1992, 1649-1652.
Figure 1. Structures of allosamidin and allosamizoline (1).
to which a hydroxymethyl group is attached.4 Besides the cyclopentane ring of 1, the cyclopentane rings of pactamycin,5 bacteriohopane,6 and aristeromycin7 have been proved to be biosynthesized from glucose. In the cyclopentane ring formation of 1, pactamycin and bacteriohopane, the hydroxymethyl carbon originates from C-6 of D-glucose, and C-C bond formation occurs between C-5 and C-1 of D-glucose. On the other hand, the C-1 carbon of D-glucose is the origin of the hydroxymethyl carbon in the case of the cyclopentane ring of aristeromycin, in which a C-C bond formation occurs between C-2 and C-6 (4) Jenkins, G. N.; Turner, N. J. Chem. Soc. Rev. 1995, 169-176. (5) Weller, D. D.; Rinehart, K. L., Jr. J. Am. Chem. Soc. 1978, 100, 6757-6758. (6) Flesch, G.; Rohmer, M. Eur. J. Biochem. 1988, 175, 405-411. (7) Parry, R. J.; Bornemann, V.; Subramanian, R. J. Am. Chem. Soc. 1989, 111, 5819-5824.
10.1021/jo001629n CCC: $20.00 © 2001 American Chemical Society Published on Web 04/19/2001
Cyclopentane Ring Formation of Allosamizoline
J. Org. Chem., Vol. 66, No. 10, 2001 3357
Table 1. Deuterium Incorporation into Allosamine and Allosamizoline Moieties of Allosamidin Derived from 2H-Labeled Glucosamines increased % of monolabeled moleculesa labeled glucosamine
in allosaminitol hexaacetate
in allosamizoline triacetate
3-2H 4-2H 5-2H 6,6-2H2
12.5 10.9 10.9 2.7 (14.0c)
14.6 8.4 b 3.7 (b,c)
a Calibrated from CI-MS spectra of labeled and nonlabeled samples. b Increase was not observed (
